Heretofore, holography technology capable of causing an observer to perceive a three-dimensional object has been used. Since holography technology does not require a special device and the like and can cause an observer to intuitively and correctly perceive a 3D object without imposing a strain on the eye of the observer, holography technology has a wide range of applications. For example, holography technology is used in the fields of exhibition, advertisement, medical care, education, entertainment, and the like.
The principle of holography technology will be described. FIG. 6 shows an example of a hologram optical generation system 60 for optically generating a hologram pattern. The hologram optical generation system 60 includes a lighting fixture 610, a light-emitting device 620, a hologram 630, and a light-emitting device 640. First, the hologram optical generation system 60 performs the processing below in order to generate the interference of light (S62). The lighting fixture 610 irradiates light to an object 600 to be displayed. The object 600 reflects the light irradiated from the lighting fixture 610 as an object beam onto the hologram 630. The light-emitting device 620 irradiates a reference beam to the hologram 630. Thus, interfering light in which the object and reference beams interfere with each other is generated.
The hologram 630 records the wavelength and phase of the interfering light generated in S62 as an interference pattern (S64). For example, the hologram 630 is a predetermined optical film and is exposed to the interfering light to record the wavelength and phase of the interfering light. The light-emitting device 640 irradiates the reference beam to the hologram 630 (S66). The hologram 630 diffracts the reference beam irradiated from the light-emitting device 640 with the interference pattern and reflects the reference beam as a reconstructed beam toward an observer. The observer perceives the wavelength and phase of light recorded on the hologram 630 by observing the reconstructed beam (S68). Thus, the observer can perceive a 3D object 650, which is the same as the object 600.
In what follows, consideration is given to the following documents:    Non-patent Literature 1) High-Speed Holographic-Stereogram Calculation Method Using 2D FFT, SPIE, Vol. 3010, p 49    Non-patent Literature 2) Recurrence formulas for fast creation of synthetic three-dimensional hologram, Applied Optics, Vol. 39, No. 35, p 6587
Moreover, in recent years, with the progress of computers and the trend toward higher definitions of LCD panels, a method of generating a hologram pattern using a computer to display the hologram pattern using an LCD panel is receiving attention (e.g., refer to Non-patent Literature 1 and Non-patent Literature 2). Known methods are divided into, for example, the following two groups:
Method 1
An object is regarded as a set of point light sources. Then, for each point light source, Fresnel-Kirchhoff integral, which determines a light wave coming from the point light source, is calculated.
Method 2
For each of cross sections when an object is divided into planes perpendicular to the depth direction, a diffraction pattern, e.g., a Fraunhofer diffraction pattern, a Fresnel diffraction pattern, or a Fourier diffraction pattern, generated by light coming from the relevant cross section, is integrated in the depth direction.
In general, optically manufacturing a hologram pattern requires various equipment, e.g., a device for generating a predetermined reference beam, a film for recording an interference pattern, a darkroom for exposing a hologram, and the like. In particular, optically manufacturing a hologram for reconstructing a moving image requires enormous cost and time.
Moreover, a known method of electronically generating a hologram also requires enormous computation time. For example, in a known two-dimensional image, each pixel is related to each portion of an object to be displayed. On the other hand, each pixel of a hologram pattern needs to record interfering light of a light wave coming from the entire object to be displayed. Accordingly, the creation of a hologram pattern requires more calculations compared with the case where general three-dimensional computer graphics are generated.
For example, according to the above-described Method 1, the computation time required for the creation of a hologram is proportional to the product of the number of pixels of the hologram, the number of point light sources, and the computation time in which one point light source determines one pixel. In the case where a moving image is created by this method using a computer, computing performance as high as several petaflops is required. On the other hand, according to Method 2, computation time is proportional to the product of the computation time for determining a hologram pattern from one cross section and the number of cross sections. This method also requires computing performance of approximately 100 gigaflops to 1 teraflops.